netdev - Re: [PATCH 00/51] treewide: Switch to __pm_runtime_put

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Message-ID: <20241007222502.GG30699@pendragon.ideasonboard.com>
Date: Tue, 8 Oct 2024 01:25:02 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ulf Hansson <ulf.hansson@...aro.org>
Cc: Sakari Ailus <sakari.ailus@...ux.intel.com>,
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	Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH 00/51] treewide: Switch to __pm_runtime_put_autosuspend()

Hi Ulf,

On Tue, Oct 08, 2024 at 12:08:24AM +0200, Ulf Hansson wrote:
> On Mon, 7 Oct 2024 at 20:49, Laurent Pinchart wrote:
> > On Fri, Oct 04, 2024 at 04:38:36PM +0200, Ulf Hansson wrote:
> > > On Fri, 4 Oct 2024 at 11:41, Sakari Ailus wrote:
> > > >
> > > > Hello everyone,
> > > >
> > > > This set will switch the users of pm_runtime_put_autosuspend() to
> > > > __pm_runtime_put_autosuspend() while the former will soon be re-purposed
> > > > to include a call to pm_runtime_mark_last_busy(). The two are almost
> > > > always used together, apart from bugs which are likely common. Going
> > > > forward, most new users should be using pm_runtime_put_autosuspend().
> > > >
> > > > Once this conversion is done and pm_runtime_put_autosuspend() re-purposed,
> > > > I'll post another set to merge the calls to __pm_runtime_put_autosuspend()
> > > > and pm_runtime_mark_last_busy().
> > >
> > > That sounds like it could cause a lot of churns.
> > >
> > > Why not add a new helper function that does the
> > > pm_runtime_put_autosuspend() and the pm_runtime_mark_last_busy()
> > > things? Then we can start moving users over to this new interface,
> > > rather than having this intermediate step?
> >
> > I think the API would be nicer if we used the shortest and simplest
> > function names for the most common use cases. Following
> > pm_runtime_put_autosuspend() with pm_runtime_mark_last_busy() is that
> > most common use case. That's why I like Sakari's approach of repurposing
> > pm_runtime_put_autosuspend(), and introducing
> > __pm_runtime_put_autosuspend() for the odd cases where
> > pm_runtime_mark_last_busy() shouldn't be called.
> 
> Okay, so the reason for this approach is because we couldn't find a
> short and descriptive name that could be used in favor of
> pm_runtime_put_autosuspend(). Let me throw some ideas at it and maybe
> you like it - or not. :-)

I like the idea at least :-)

> I don't know what options you guys discussed, but to me the entire
> "autosuspend"-suffix isn't really that necessary in my opinion. There
> are more ways than calling pm_runtime_put_autosuspend() that triggers
> us to use the RPM_AUTO flag for rpm_suspend(). For example, just
> calling pm_runtime_put() has the similar effect.

To be honest, I'm lost there. pm_runtime_put() calls
__pm_runtime_idle(RPM_GET_PUT | RPM_ASYNC), while
pm_runtime_put_autosuspend() calls __pm_runtime_suspend(RPM_GET_PUT |
RPM_ASYNC | RPM_AUTO).

> 
> Moreover, it's similar for pm_runtime_mark_last_busy(), it's called
> during rpm_resume() too, for example. So why bother about having
> "mark_last_busy" in the new name too.
> 
> That said, my suggestion is simply "pm_runtime_put_suspend".

Can we do even better, and make pm_runtime_put() to handle autosuspend
automatically when autosuspend is enabled ?

> If you don't like it, I will certainly not object to your current
> approach, even if I think it leads to unnecessary churns.
> 
> [...]
> 
> Kind regards
> Uffe

-- 
Regards,

Laurent Pinchart